The objectives of this project are to understand the mechanisms which control the utilization of essential fatty acids for the synthesis of membrane phospholipids in developing tissues. Using suckling rats studies are designed to determine whether the chemical compound in which the essential fatty acids are found effect their digestion and absorption; to determine in which lipoproteins and in which lipids of the serum the essential fatty acids are transported; to determine the role of the liver in the synthesis of polyunsaturated fatty acids and the packaging of these fatty acids into lipoproteins in relation to the deposition of polyunsaturated fatty acids in brain phospholipids; to determine the nature of the serum precursor to uptake of polyunsaturated fatty acids by brain; to measure the rate of biosynthesis of the molecular species of brain phospholipids that contain polyunsaturated fatty acids in order to determine if membrane phospholipid biosynthesis in a developing tissue is different than in adult tissue; to develop in vitro systems for studying brain phospholipid biosynthesis.